Role of oocyte position in establishment of anterior-posterior polarity in Drosophila.

The polarized microtubule cytoskeleton of the Drosophila oocyte directs the localization of the maternal determinants which establish the anterior-posterior (AP) axis of the embryo. Because the formation of this microtubule array is dependent on signals from the follicle cells that surround the oocyte, it has been proposed that AP polarity originates in the follicle cells. Here it is shown that the movement of the oocyte to the posterior of the egg chamber early in oogenesis determines AP polarity in the follicle cell layer, and also in the oocyte. Moreover, the generation of AP asymmetry requires signaling from the germ line to the soma and back again.